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<title>lwres_context</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
<a name="id2476275"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2>Name</h2>
<p>lwres_context_create, lwres_context_destroy, lwres_context_nextserial, lwres_context_initserial, lwres_context_freemem, lwres_context_allocmem, lwres_context_sendrecv &#8212; lightweight resolver context management</p>
</div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<div class="funcsynopsis">
<pre class="funcsynopsisinfo">#include &lt;lwres/lwres.h&gt;</pre>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_context_create</b>(</code></td>
<td>lwres_context_t **�</td>
<td>
<var class="pdparam">contextp</var>, </td>
</tr>
<tr>
<td>�</td>
<td>void *�</td>
<td>
<var class="pdparam">arg</var>, </td>
</tr>
<tr>
<td>�</td>
<td>lwres_malloc_t �</td>
<td>
<var class="pdparam">malloc_function</var>, </td>
</tr>
<tr>
<td>�</td>
<td>lwres_free_t �</td>
<td>
<var class="pdparam">free_function</var><code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"><tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_context_destroy</b>(</code></td>
<td>lwres_context_t **�</td>
<td>
<var class="pdparam">contextp</var><code>)</code>;</td>
</tr></table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
void
<b class="fsfunc">lwres_context_initserial</b>(</code></td>
<td>lwres_context_t *�</td>
<td>
<var class="pdparam">ctx</var>, </td>
</tr>
<tr>
<td>�</td>
<td>lwres_uint32_t �</td>
<td>
<var class="pdparam">serial</var><code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em"><tr>
<td><code class="funcdef">
lwres_uint32_t
<b class="fsfunc">lwres_context_nextserial</b>(</code></td>
<td>lwres_context_t *�</td>
<td>
<var class="pdparam">ctx</var><code>)</code>;</td>
</tr></table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
void
<b class="fsfunc">lwres_context_freemem</b>(</code></td>
<td>lwres_context_t *�</td>
<td>
<var class="pdparam">ctx</var>, </td>
</tr>
<tr>
<td>�</td>
<td>void *�</td>
<td>
<var class="pdparam">mem</var>, </td>
</tr>
<tr>
<td>�</td>
<td>size_t �</td>
<td>
<var class="pdparam">len</var><code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
void
<b class="fsfunc">lwres_context_allocmem</b>(</code></td>
<td>lwres_context_t *�</td>
<td>
<var class="pdparam">ctx</var>, </td>
</tr>
<tr>
<td>�</td>
<td>size_t �</td>
<td>
<var class="pdparam">len</var><code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
<tr>
<td><code class="funcdef">
void *
<b class="fsfunc">lwres_context_sendrecv</b>(</code></td>
<td>lwres_context_t *�</td>
<td>
<var class="pdparam">ctx</var>, </td>
</tr>
<tr>
<td>�</td>
<td>void *�</td>
<td>
<var class="pdparam">sendbase</var>, </td>
</tr>
<tr>
<td>�</td>
<td>int �</td>
<td>
<var class="pdparam">sendlen</var>, </td>
</tr>
<tr>
<td>�</td>
<td>void *�</td>
<td>
<var class="pdparam">recvbase</var>, </td>
</tr>
<tr>
<td>�</td>
<td>int �</td>
<td>
<var class="pdparam">recvlen</var>, </td>
</tr>
<tr>
<td>�</td>
<td>int *�</td>
<td>
<var class="pdparam">recvd_len</var><code>)</code>;</td>
</tr>
</table>
</div>
</div>
<div class="refsect1" lang="en">
<a name="id2543531"></a><h2>DESCRIPTION</h2>
<p><code class="function">lwres_context_create()</code>
      creates a <span class="type">lwres_context_t</span> structure for use in
      lightweight resolver operations.  It holds a socket and other
      data needed for communicating with a resolver daemon.  The new
      <span class="type">lwres_context_t</span> is returned through
      <em class="parameter"><code>contextp</code></em>, a pointer to a
      <span class="type">lwres_context_t</span> pointer.  This
      <span class="type">lwres_context_t</span> pointer must initially be NULL, and
      is modified to point to the newly created
      <span class="type">lwres_context_t</span>.
    </p>
<p>
      When the lightweight resolver needs to perform dynamic memory
      allocation, it will call
      <em class="parameter"><code>malloc_function</code></em>
      to allocate memory and
      <em class="parameter"><code>free_function</code></em>
      to free it.  If
      <em class="parameter"><code>malloc_function</code></em>
      and
      <em class="parameter"><code>free_function</code></em>
      are NULL, memory is allocated using
      <span class="citerefentry"><span class="refentrytitle">malloc</span>(3)</span>.
      and
      <span class="citerefentry"><span class="refentrytitle">free</span>(3)</span>.

      It is not permitted to have a NULL
      <em class="parameter"><code>malloc_function</code></em> and a non-NULL
      <em class="parameter"><code>free_function</code></em> or vice versa.
      <em class="parameter"><code>arg</code></em> is passed as the first parameter to
      the memory allocation functions.  If
      <em class="parameter"><code>malloc_function</code></em> and
      <em class="parameter"><code>free_function</code></em> are NULL,
      <em class="parameter"><code>arg</code></em> is unused and should be passed as
      NULL.
    </p>
<p>
      Once memory for the structure has been allocated,
      it is initialized using
      <span class="citerefentry"><span class="refentrytitle">lwres_conf_init</span>(3)</span>
      and returned via <em class="parameter"><code>*contextp</code></em>.
    </p>
<p><code class="function">lwres_context_destroy()</code>
      destroys a <span class="type">lwres_context_t</span>, closing its socket.
      <em class="parameter"><code>contextp</code></em> is a pointer to a pointer to the
      context that is to be destroyed.  The pointer will be set to
      NULL when the context has been destroyed.
    </p>
<p>
      The context holds a serial number that is used to identify
      resolver request packets and associate responses with the
      corresponding requests.  This serial number is controlled using
      <code class="function">lwres_context_initserial()</code> and
      <code class="function">lwres_context_nextserial()</code>.
      <code class="function">lwres_context_initserial()</code> sets the serial
      number for context <em class="parameter"><code>*ctx</code></em> to
      <em class="parameter"><code>serial</code></em>.
      <code class="function">lwres_context_nextserial()</code> increments the
      serial number and returns the previous value.
    </p>
<p>
      Memory for a lightweight resolver context is allocated and freed
      using <code class="function">lwres_context_allocmem()</code> and
      <code class="function">lwres_context_freemem()</code>.  These use
      whatever allocations were defined when the context was created
      with <code class="function">lwres_context_create()</code>.
      <code class="function">lwres_context_allocmem()</code> allocates
      <em class="parameter"><code>len</code></em> bytes of memory and if successful
      returns a pointer to the allocated storage.
      <code class="function">lwres_context_freemem()</code> frees
      <em class="parameter"><code>len</code></em> bytes of space starting at location
      <em class="parameter"><code>mem</code></em>.
    </p>
<p><code class="function">lwres_context_sendrecv()</code>
      performs I/O for the context <em class="parameter"><code>ctx</code></em>.  Data
      are read and written from the context's socket.  It writes data
      from <em class="parameter"><code>sendbase</code></em> &#8212; typically a
      lightweight resolver query packet &#8212; and waits for a reply
      which is copied to the receive buffer at
      <em class="parameter"><code>recvbase</code></em>.  The number of bytes that were
      written to this receive buffer is returned in
      <em class="parameter"><code>*recvd_len</code></em>.
    </p>
</div>
<div class="refsect1" lang="en">
<a name="id2543719"></a><h2>RETURN VALUES</h2>
<p><code class="function">lwres_context_create()</code>
      returns <span class="errorcode">LWRES_R_NOMEMORY</span> if memory for
      the <span class="type">struct lwres_context</span> could not be allocated,
      <span class="errorcode">LWRES_R_SUCCESS</span> otherwise.
    </p>
<p>
      Successful calls to the memory allocator
      <code class="function">lwres_context_allocmem()</code>
      return a pointer to the start of the allocated space.
      It returns NULL if memory could not be allocated.
    </p>
<p><span class="errorcode">LWRES_R_SUCCESS</span>
      is returned when
      <code class="function">lwres_context_sendrecv()</code>
      completes successfully.
      <span class="errorcode">LWRES_R_IOERROR</span>
      is returned if an I/O error occurs and
      <span class="errorcode">LWRES_R_TIMEOUT</span>
      is returned if
      <code class="function">lwres_context_sendrecv()</code>
      times out waiting for a response.
    </p>
</div>
<div class="refsect1" lang="en">
<a name="id2543769"></a><h2>SEE ALSO</h2>
<p><span class="citerefentry"><span class="refentrytitle">lwres_conf_init</span>(3)</span>,

      <span class="citerefentry"><span class="refentrytitle">malloc</span>(3)</span>,

      <span class="citerefentry"><span class="refentrytitle">free</span>(3)</span>.
    </p>
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